Changes in the Nitrogen Reserves of Apple Shoots During the Dormant Season

Abstract

Nitrogen levels were measured in 1-year-old shoot wood and bark of 2-year-old Golden Delicious apple trees from January to April. Nitrogen reserves were found mainly to be in the protein fraction of both wood and bark. These reserves were hydrolysed in mid-late March resulting in a rapid increase in the soluble nitrogen levels for use in growth. Prior to hydrolysis of protein there appeared to be a significant amount of soluble nitrogen present especially in wood. Arginine composed 8-17 % of the total free amino fraction in bark and 20-30 % in wood. It appears that arginine and the supplementary amino acids and amides may also make up a nitrogen reserve, especially in wood.